Exoplanets and asteroseismology: know the star, know the planet

This thesis primarily considers evolved exoplanetary systems through the use of asteroseismology as a tool to investigate the fundamental properties of the host stars, and the inferred planetary parameters. Of particular interest are the masses of evolved stars, and investigating how the available observables may bias the recovered mass estimates. Accurate and precise stellar masses are of critical importance. Whilst most of this work considers ensemble analysis, where relevant individual systems are considered, including a binary star system with an M dwarf and an asteroseismic red giant primary star. Another system of note is a transiting gas giant orbiting a red giant host, that will be consumed by the expansion of the host star. The metallicity distributions of evolved exoplanet hosts, and a suitable ensemble of field stars are also investigated using spectroscopy. This is to determine if evolved giant planet exoplanet hosts display the same metallicity excess seen in main sequence giant planet hosts. We fail to find a statistically significant excess in metallicity. Finally the noise properties of evolved stars are considered, including predicting the noise properties from stellar parameters, and how the elevated noise levels in evolved stars impact the detectable of planets around them.